1. Field of the Invention
The present invention relates to a four-way directional control valve, and particularly to a four-way directional control valve designed to switch between several refrigerant lines, e.g. in a heat pump type air conditioning system for an automotive vehicle, e.g., to switch between a state where a pipe A communicates with a pipe D while a pipe B communicates with a pipe C and another state where said pipe A communicates with pipe C while pipe B communicates with pipe D.
2. Description of the Related Art
According to U.S. Pat. No. 4,805,666 a four-way directional control valve of a refrigerating cycle includes a flat valve seat formed with several openings communicating with respective pipes and a hemispherical valve slider slidably arranged on said valve seat. Sliding of said valve slider switches between the different states of communications between the pipes. Said valve slider and said valve seat need to be formed of solid material and need to have excellent sliding performance and a very high precision flatness at a mirror surface level in order to prevent leakage. Said components are costly to manufacture. A rubber sealing or the like cannot be used, because that material suffers from abrasion when said components are slid on each other.
Earlier European patent application EP-A-0927846, published after the priority date of the present application, proposes a four-way directional control valve capable of performing positive four-way directional control or four pipes without needing very high precision sealing components but with a combination of components at a normal precision level. Between two axially aligned oppositely facing valve seats first and second hollow and coaxial cylindrical valve elements are arranged in an axially moveable manner. First and second coaxial and flat valve closure elements are associated to and urged against said valve seats from their axial outer sides. Each valve seat defines together with an associated to partition wall a connecting portion communicating with one of said pipes, while within said casing a first pipe is communicating with a common high pressure passage extending to both valve seats. Both cylindrical valve elements penetrate said partition walls and alternatingly co-operate with said first and second valve closure elements in order to let them be seated on the respective valve seat or to lift them. Stationary further partition walls confine an isolated low pressure chamber communicating with a second pipe. Both cylindrical hollow valve elements are open towards said isolated low pressure chamber. Each cylindrical hollow valve element carries a separator wall defining a ring piston located within a respective first and second pressure regulating chamber. The pressures in said first and second pressure regulating chambers are varied by a solenoid actuated pilot valve adapted to alternatingly vent one of first and second pressure regulating chambers into said isolated low pressure chamber, while both first and second pressure regulating chambers permanently are connected to said common high pressure passage via orifices. Said proposed control valve design has a plurality of axially arranged spaces, namely nine spaces among which some are constantly are under high pressure while others are under medium or even under low pressure. The design needs a plurality of components and particularly a large number of sliding sealing portions for the cylindrical hollow valve elements. There are six sealing portions where during a relative axial motion has to be sealed, and eighth stationary sealing portions, each containing at least one resilient sealing element, resulting in an increase in manufacturing efforts and costs.